This invention relates to a method and a device for arc welding, and to a method of surfacing a metal article using the device.
More specifically, the invention concerns a method and device for the protective surfacing or coating (commonly known as overlaying) of the interior of a hollow structure. The most common use of the device is to surface the inner wall of a pipe having an interior diameter of at least one inch.
The conventional method of surfacing the inner surface of tubular articles is to use apparatuses including a curved head or "goose neck" for directing filler metal towards a tip. One method of surfacing the interior of a pipe is to insert a welding tool into the pipe and to rotate the pipe to form an annular metal strip. The pipe or welding tool is then advanced, and another strip is applied to the pipe. This method is quite slow, particularly on large pipes, since the weld head must solidify to avoid flowing during pipe rotation.
Another method of surfacing or coating the interior of a small diameter pipe is the insertion of a liner or sleeve into the pipe, followed by welding of the sleeve and pipe at the ends thereof. Because of the different coefficients of expansion of the pipe and sleeve, this method is unsatisfactory.
There are many machines or apparatuses for welding the interior of tubular articles described in the patent literature. Examples of such machines or apparatuses are found in U.S. Pat. Nos. 1,555,034, which issued to A. M. Stanley et al on Sep. 29, 1925; 2,606,267, which issued to T. McElrath, Jr. on Aug. 5, 1952; 3,018,360, which issued to R. D. Engel on Jan. 23, 1962; 3,265,856, which issued to S. Cecil on Aug. 9, 1966; 3,305,664, which issued to M. M. Kensrue on Feb. 21, 1967; 3,397,298, which issued to I. V. Nelson on Aug. 13, 1968; 3,463,902, which issued to W. A. Bircher on Aug. 26, 1969; 3,836,747, which issued to P. M. Wlos on Sep. 17, 1974; 4,215,809, which issued to D. L. Davis on Aug. 5, 1980; 4,379,963, which issued to G. Kazlauskas on Apr. 12, 1983; 4,571,475, which issued to G. B. Rabe on Feb. 18, 1986; 4,727,238, which issued to R. N. Mann on Feb. 23, 1988 and 4,731,518, which issued to D. R. Parmelee et al on Mar. 15, 1988. Many of these patents disclose relatively complicated devices, some of which are of the goose neck type described above.
An object of the present invention is to provide a relatively simple device for performing arc welding on the interior of an article such as a pipe.
Another object of the invention is to provide a simple, efficient method of surfacing the interior of a hollow article using the device described herein.
A further object of the invention is to provide a method of surfacing the interior of a hollow article by welding such that substantially "smooth" weld is produced which serves to reduce the possibility of weld deposit defects commonly occurring by virtue of irregular weld deposits.